Effects of dipyridamole and adenosine infusions on ovine pulmonary
and systemic circulations .
Skimming, Jeffrey W., Vincent G. Demarco, and Sidney Cassin.
DEPARTMENTS OF PHYSIOLOGY, AND PEDIATRICS AT THE UNIVERSITY OF
FLORIDA COLLEGE OF MEDICINE; GAINESVILLE, FLORIDA 32610
APStracts 3:0385H, 1996.
This study was designed to test the hypothesis that A2 adenosine
receptors mediate the hemodynamic responses to intravenous infusions
of dipyridamole. We tested the hypothesis using theophylline which
has been reported to block A2 adenosine receptors and thereby
attenuate the vasodilation caused by adenosine. Twenty four
anesthetized lambs that were between 7 and 17 days of age were used.
Basal vascular tone of each animal was increased with the
thromboxane-mimetic U46619. A theophylline dose commonly used in
humans (5.0 mg/k infused over 30 min followed by 1.0 mg/k/h) resulted
in negligible changes in the vasodilation caused by either
dipyridamole or adenosine. However, a tenfold greater theophylline
dose significantly attenuated the vasodilation caused by adenosine,
yet the attenuation in vasodilation caused by dipyridamole remained
negligible. In addition, dipyridamole caused a weakly preferential
pulmonary vasodilation whereas adenosine caused a strongly
preferential systemic vasodilation. These findings suggest that
dipyridamole dilates effectively both the pulmonary vasculature and
the systemic vasculature via predominantly adenosine-independent
mechanisms.
Received 12 March 1996; accepted in final form 21 August 1996.
APS Manuscript Number H236-6.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1996 The American Physiological Society.
Published in APStracts on 19 September 1996